15. THYANENSIS, a geometrician of profound abilities, if we may judge from the subject of his writings, which regarded the most transcendental parts of ancient geometry, the consideration of curve lines.
In particular, he investigated the lines formed by the intersection of a plane with certain curved surfaces.
These lines are called by Pappus πλεκτοίδες
iv. post prop. 40).
The nature of the surfaces or the lines is unknown; but Pappus informs us that their investigation excited the admiration of many geometricians; among others, of Menelaus of Alexandria. As Menelaus was in Rome A. D. 98, Philon must have preceded him. (Montuela, vol. i. p. 316.)